JP3583887B2 - Memory card - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a memory card.
[0002]
[Prior art]
At present, in electronic devices such as personal computers, card-shaped memories such as those described in JP-A-5-242666 (G11C5 / 14), JP-A-8-227385 (G06F12 / 16), etc. The function can be extended by making it detachable via a main board or detachable from the main board.
[0003]
As a memory element used in this type of memory card, an SRAM (Static Random Access Memory) is generally used in consideration of easiness of rewriting and memory retention. In addition, as described in Japanese Patent Application Laid-Open No. 8-227385, this type of memory card has a voltage supplied from an electronic device to which the memory card is attached, and a battery incorporated in the memory card. The memory element can be backed up. Therefore, even when the memory card is removed from the electronic device, the memory contents are retained and can be reused.
[0004]
[Problems to be solved by the invention]
However, the fact that the contents of the memory are retained even when detached from the electronic device in this way means that a third party can steal the memory card and easily read the contents, and the confidentiality is low. Had a lot of problems.
[0005]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a memory element, a backup battery, at least a first terminal for receiving a drive voltage supplied from the outside, and an external terminal that permits supply of the drive voltage to the memory element. An external connection connector having a second terminal for receiving the external permission signal, a switch group having a plurality of contacts, and detecting a state of each contact of the switch group to supply a drive voltage to the memory element. Means for outputting an internal permission signal to be permitted, one end connected to the memory element, the other end connected to the backup battery and the first terminal, and in response to either the external or internal permission signal And a switching circuit for turning on.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a circuit diagram showing an embodiment of a memory card 1 to which the present invention is applied. This card 1 is used for external connection for detachably electrically connecting to a main board of an electronic device or the like (not shown). Connector 2, first and second backflow prevention diodes 3, 4, battery 5, memory element 6 composed of SRAM, switch group 7 composed of a plurality of dip switches, and detection for detecting the state of each switch of the switch group 7. A circuit 8, for example, a first switching circuit 9 including a switching transistor, for example, a second switching circuit 10 including a switching transistor, and a discharging unit 12 including a discharge resistor 11 are provided.
[0007]
The connector 2 has a plurality of terminals for making an electrical connection with an electronic device. One of the terminals (hereinafter, referred to as a first terminal) 13 receives a drive voltage supplied from the electronic device. And another terminal 14 (hereinafter, referred to as a second terminal) 14 is for receiving a permission signal supplied from the electronic device.
[0008]
The first terminal 13 is connected to one terminal of the first switching circuit 9 via the first backflow prevention diode 3. A battery 5 is also connected to this one terminal via a second backflow prevention diode 4.
[0009]
The other terminal of the first switching circuit 9 is connected to the SRAM 6. Therefore, when the switching circuit 9 is turned on, a voltage is supplied to the SRAM 6, and the memory contents of the SRAM 6 can be held.
[0010]
The first switching circuit 9 is connected to the second terminal 14 and the detection circuit 8, and is turned on only when a permission signal is supplied from at least one of the second terminal 14 and the detection circuit 8.
[0011]
The detection circuit 8 outputs the permission signal only when the contact of each DIP switch of the switch group 7 is in a predetermined state. Therefore, when the memory card 1 is removed from the electronic device and each of the contacts of the switch group 7 is not in the predetermined state, the permission signal is not supplied to the first switching circuit 9 so that the circuit 9 is turned off. As a result, the memory contents of the SRAM memory element 6 cannot be held.
[0012]
The discharging means 12 is connected to the SRAM memory element 6. When the second switching circuit 10 is turned on, the charge stored in the memory element 6 is discharged via the discharging resistor 11. The second switching circuit 10 is also connected to the second terminal 14 and the detection circuit 8, and is turned on only when the permission signal is not supplied from any of the second terminal 14 and the detection circuit 8.
[0013]
That is, in the memory card 1 of the present embodiment, if the contacts of the switches of the switch group 7 are not kept in a predetermined state when being removed from the electronic device, the memory element 6 will not be backed up after the removal and the memory contents will be lost. It becomes.
[0014]
Further, in the present embodiment, immediately after the supply of the driving voltage to the memory element 6 is stopped, the accumulated charge of the memory element 6 is discharged by the discharging means 12, so that even if the capacity of the capacitor constituting the memory element 6 is large, the electric charge is rapidly reduced Memory erasure becomes possible.
[0015]
【The invention's effect】
As is clear from the above description, according to the present invention, even if only the memory card is stolen by a third party, the switch group in the memory card is set to a state other than the predetermined state, so that the memory is stolen when the memory card is stolen. Since the contents are erased, the confidentiality of the memory contents to a third party can be increased.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Memory card 2 Connector 5 Battery 6 SRAM memory element 7 Switch group 8 Detection circuit 12 Discharge means 13 First terminal 14 Second terminal

Claims (1)

A memory device, a backup battery, a first terminal for receiving at least a drive voltage supplied from outside, and a second terminal for receiving an external permission signal from outside for permitting supply of the drive voltage to the memory device An external connection connector having a switch group having a plurality of contacts, a means for detecting a state of each contact of the switch group, and outputting an internal permission signal for permitting supply of a drive voltage to the memory element, A switching circuit connected at one end to the memory element and connected at the other end to the backup battery and the first terminal and turned on in response to either the external or internal permission signal; And a memory card.

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